Watercraft



0. REDER WATERCRAFT Feb. 28, 1967 4 Sheets-Sheet 1 Filed Feb. ll, 1966 FIG. 2

INVENTOR. Otto Peder Feb. 28, 1967 o. REDER 3,306,246

WATERG RAFT Filed Feb. 11, 1966 4 Sheets-$heet 3 V: 0, top view y= 90 side view l =270 side view A FIG'Q INVENTOR. 0t t o Peder 0. REDER WATERCRAFT Feb. 28, 1967 Filed Feb.

4 Sheets-Sheet 4 range blade root ,v mag blade radius R FIG. 13

INVENTOR. a 7 0A?- United States Patent 7 Claims. ci. 114-665) This is a continuation-in-part application of my copending patent application Ser. No. 360,142, filed April 15, 1964, now abandoned and entitled Watercraft and Method of Driving Same.

The present invention relates to watercraft and, more particularly, concerns an arrangement for producing a lift and propulsion for ships, especially ships the hull of which has to be lifted from the water at higher speeds of the ship.

It is known to propel a watercraft by marine propellers and to produce the lift force for lifting the hull of the Watercraft out of the water by the flow of water around hydrofoils and hydrofoil bodies. By arranging the marine propeller at an incline with regard to the direction of flow of the water a minor lifting force may be produced, as a component of the forward thrust, however, this component is completely insuflicient for lifting the hull of a ship out of the water.

The employment of ordinary propellers for producing the propelling force of a ship in combination with hydrofoils or hydrofoil bodies for producing the lift force for lifting the hull of the ship out of the water at higher speeds has serious disadvantages. Among others, there may be mentioned the fact that at rough seas the hydrofoils may partially or completely be lifted out of the water and upon reentry shock-like forces will be created on the ship which seriously affect the maneuverability, and the riding comfort of the passengers.

Furthermore, at the onset of cavitation the flow of water around the hydrofoils interferes with that around the propeller blades and vice versa.

It is, therefore, an object of the present invention to overcome the above outlined disadvantages.

It is another object of the present invention to provide a new method of driving a water craft especially of driving a ship the hull of which has to be lifted from the Water at higher speeds of the ship.

It is still another object of the persent invention to completely eliminate hydrofoils or hydrofoil bodies for producing the lift force for lifting the hull of a watercraft out of the water.

It is a still further object of the present invention to eliminate the dangerous interference of hydrofoils and propellers when cavitation occurs during the operation of the watercraft.

These and other objects and advantages of the invention will appear more clearly from the following specification in connection with the accompanying drawings, in which: a

FIG. 1 diagrammatically illustrates a side view of a watercraft equipped with propelling means in conformity with the present invention.

FIG. 2 is a front view of the watercraft of FIG. 1.

FIG. 3 similar to FIG. 1 shows a side view of a watercraft which differs, however, from that of FIG. 1 in that the propeller is not in the rear portion but in the front portion of the streamlined body supporting the propeller.

FIG. 3a shows on a somewhat larger scale than FIG. 3 the portion within the dot-dash circle of FIG. 3.

FIG. 3b, 3c and 3d respectively illustrate different profiles of rotor blades for use in connection with the propelling means according to the present invention.

3,306,246 Patented Feb. 28, 1967 FIG. 4 shows a ship equipped with propelling means according to the present invention in submerged condition.

FIG. 5 shows the means for adjusting the angle of incidence of the propeller.

FIG. 6 illustrates means for tilting the propeller supporting struts.

FIGS. 7 to 10 illustrate vector diagrams of velocities and forces 'acting at sections through propeller blades of a tangential lift force propeller according to the present invention.

FIGS. 11 and 12 illustrate the distribution of the tangential and aixal forces acting on the blades of the propeller according to the present invention.

FIG. 13 illustrates diagrammatically the ranges of blade settings and blade twists suitable for the tangential lift force propeller according to the present invention.

The watercraft according to the present invention, which operates with its hull lifted above the water during normal operation, is characterized primarily in that the heretofore necessary combination of two means for propelling the craft and for lifting the hull above the water,

, namely the combination of ordinary propulsion screws with hydrofoils has been replaced by one single means in the form of one or several tangential lift force propellers. This special type propeller produces the propelling force for the watercraft and at the same time the force required for lifting the hull of the craft above the water, thus performing a double function and forming so to speak a rotating hydrofoil. This special type propeller will be discussed in detail further below and under no circumstances must be confused with an ordinairy marine propeller or propulsion screw. The main difference consists in that ordinary marine propellers or propulsion screws produce mainly a forward thrust and only a minor lift force as a component of the forward thrust, whereas the water having been acted upon by a tangential lift force propeller has a large downwardly directed component behind the plane of rotation of the propeller with the result that in addition to the propulsion also a large lift force is created.

With the watercraft according to the present invention the arrangement may be such that one or more tan-gential lift force propellers produce the lift and propulsion forces for the craft. It is furthermore possible that out of a plurality of propellers of the above mentioned type only one or some are driven by a power plant whereas the remaining propellers are autorotating. Thus the propulsion force may be produced by the driven propellers while the lift force is produced by the autorotating propellers.

According to a further feature of the present invention the normal force propeller or propellers may be employed for producing a negative lift for purposes of submerging a watercraft. Referring now to the drawings in detail and FIGS. 1 and 2 thereof in particular, the ship shown therein has a hull 1 which has connected thereto struts 2 the lower ends of which carry normal force or tangential lift force propellers 3. These propellers 3 have their axes of rotation inclined at an angle with regard to the flow direction, and have at least four blades. When a relative flow exists between the water and the propellers, the latter produce a lift which, in addition to being dependent on other factors, is also dependent on the angle on. A positive or negative angle of incidence on within the range of from 5 to 20 has proved highly successful.

The said propellers may rotate freely or may be driven by a certain or freely variable input power. If the propellers are not driven, they will furnish a drag, however, the ratio of lift to drag C /C is still very favorable. According to a particularly advantageous embodiment of the invention, only the stern propeller may be driven while the two bow propellers are autorotating.

For steering and trimming purposes a boat may, in conformity with the present invention, be equipped with normal force propellers the inclination of the axis of rotation of which may be variable relative to the flow direction. If under these circumstances, the axis of rotation is slightly negatively inclined, a negative lift may be produced for submerging a watercraft.

An arrangement of this type is shown in FIGS. 3 and 4. As will be seen from FIG. 3, the axis of rotation a of the propeller confines a positive angle with the flow direction, wit-h the result that a positive lift is produced and the hull of the ship 1 is lifted out of the water.

According to FIG. 4, the axis of rotation of the propeller has a negative angle of incidence so that a negative lift results and the ship can quickly submerge. In other words, by a mere changing of the angle at of the water propellers, the ship can quickly submerge without requiring flooding of Water-tanks or the like.

This variation of the angle a can easily be effected by either tilting the streamlined body 4 carrying the propeller or by tilting the struts 2 which carry the streamlined body 4 with the propellers 3 about an axis B-B (FIG. 2). An arrangement for tilting the streamlined body 4 is shown in FIG. 5. According to FIG. 5, the streamlined body 4 is by means of a joint 29 connected to the strut 2. Body 4 may be turned about its respective pivot by means of a control bar 6. The drive shaft 7 drives propeller 3 through a universal joint 8 and bevel gears 9, 10.

An arrangement for tilting the axis of rotation of the propeller by means of the struts 2 is shown in FIG. 6. According to this arrangement, a worm wheel 12 is connected to strut 2 so that said worm wheel is coaxial with the pivot 11 about which strut 2 is pivotable. Worm wheel 12 is in mesh with a Worm 13 which is drivingly connected to a motor 14. By rotating the shaft of motor 14 in one direction or the other, the struts may be tilted forwardly or backwa-rdly.

According to a further development of the invention, it is, of course, also possible to combine both the arrangement of FIG. and the arrangement of FIG. 6 so that one arrangement may be used for trimming purposes when center-of-gravity displacements are involved. The arrangement for upwardly tilting the struts 2 is also advantageous for maneuvering in a harbor and for purposes of inspection and repair. In addition to having the struts tiltable forwardly and backwardly about the axis BB, it is also possible to have the struts tiltable about the axis A-A of FIG. 1. This can be done by providing a universal joint similar to that shown in FIG. 5 for the tiltability of the streamlined body 4 relative to the strut 2.

The operation of the special type propeller used in the watercraft according to the present invention will become more readily apparent from the diagrammatical illustrations of FIGS. 7 through 13.

FIG. 13 diagrammatically illustrates the most suitable ranges of the blade settings and blade twists for the tangential lift force propellers. The blade incidence 5 against the plane of rotation is conventionally measured at a distance of 70% of the blade radius, and will be selected within the range of from 45 to 75 in conformity with the requirements of driven or autorotating propellers. The blade twist AS is the difference of incidences between the root and the tip of the blades. Also angle A2 will be selected in conformity with specific requirements and will suitably range between AS-=30 and A5-=2.

FIGS. 7 through show vector diagrams of velocities and forces acting at a section through a motor-driven propeller blade at about 70% of the radius, while FIGS. 11 and 12 represent perspective views of the distribution of the tangential and axial fiuid loads along four blades positioned at the quadrants x/=0, 90, 180 and 270.

As an example for the tangential lift force propeller a characteristic example has been illustrated in FIGS. 7 through 12. The special features of this propeller are the following. The angle of incidence a of the axis of the propeller with regard to the direction of motion v is within the range of from 5 to 20; the angle of incidence 5 against the plane of rotation at 70% of the radius is within the range of from 45 to 75 while the propeller is driven by a torque f such magnitude that the circumferential speed a at the mentioned section is smaller than the forward speed v, the preferred ratio being v/u=l.0 to 2.5; the blade section is a wedge type super-cavitating profile, preferably a symmetrical uncambered bi-concave profile.

FIGS. 7 and 9 show a section through the blades positioned at =0 and =180 respectively, as viewed from the top. The forward speed v and the circumferential speed a form the resultant speed w of the section with regard to the water. As can be seen from these figures, a resultant force F at an angle slightly larger than acts on the section. This force can be resolved into the axial force A and the tangential force T in the plane of rotation.

FIGS. 8 and 10 show a section through a blade at =90 and \//=270 as viewed from the tip of the blade positioned at 11/:90". In these figures the angle of incidence 0c of the propeller axis is clearly visible. As before the forward speed v and the circumferential speed it combine to the resultant speed w. The resultant fluid force F acts at an angle slightly larger than 90 with ragard to the section. Again, this force can be resolved into the axial force A and the tangential force T. As is clearly shown in FIGS. 8 and 10 the tangential force T in the angle positions =90 and =270 is in both cases directed upwardly with a mainly vertically directed component.

If the forces acting at various sections along the blades in the various quadrants are calculated, the distribution of fluid loads as shown in FIGS. 11 and 12 is obtained. FIG. 11 shows the distribution of the blade loads T in tangential direction i.e. in the plane of rotation whereas FIG. 12 shows the blade loads in axial direction, i.e. parallel to the axis of rotation.

The most important effect that can be derived from FIG. 11 is that the blade loads in the quadrants of 1p=90 and =270 are mainly vertically upwardly directed. It is the summation of these vertical loads which will produce the resultant tangential lift force which has a sufficient lift component to lift the hull of a ship out of the water. Similarly, it can be seen from FIG. 12 that the summation of all axial loads will produce a forwardly directed propulsion force.

It may be repeated that FIGS. 7 through 12 illustrate the distribution of the loads for a motor driven propeller. For the case of not mechanically driven propellers, i.e. autorotating propellers it can also be shown that mainly upwardly directed tangential loads are obtained in the quadrants b=90 and tp=270 which are sufiicient to lift a hull out of the water. In this case the sum of the moments due to tangential loads about the axis of rotation becomes 0, which is the condition for autorotation and the axial forces are directed rearwardly indicating a drag which has to be overcome by the driven propellers of the ship.

It is important for tangential lift force propellers employed for propelling the watercraft according to the present invention and for lifting the hull thereof above the water level, to obtain upwardly directed tangential loads on the blades in the region of the quadrants =90 and especially for the quadrant =270. Therefore, strongly cambered profiles and blades having large chords covering a large areas of the quadrants, as used on ordinary propulsion propellers, would spoil this effect. This is the reason why customary propulsion propellers even if arranged at an angle of incidence a with regard to the direction of flow will not produce the same result i.e. will not produce the necessary lift.

Referring now to the shape of the blades of the propeller, advantageously, according to the present invention, a cavitating profile is employed for the profile of the propeller blades, so that the propellers will at the rated speed rotate in a fully cavitating manner. More specifically referring to FIG. 3, it will be seen therefrom how supercavitating water propellers may be employed in connection with the present invention. Propellers 3 are employed as tractor propellers so that a portion of the struts 2 will be located within the range of the cavitation slip stream whereby the drag of the strut will be reduced. The propellers themselves will operate in an undisturbed flow.

FIG. 3a shows how the wedge-shaped blade profile provided with sharp front edges is so adjusted as to have a high angle of incidence 0:. This angle cc is selected within the range of from 25 to 90, preferably within the range of from 45 to 75 at 70% of the radius, depending on the advance ratio of the propeller. The angle of incidence or may, if necessary, be changed in operation by an adjusting device, as disclosed, for instance, in US. Patents 3,056,457 and 2,931,443.

The well-known wedge profiles shown, for instance in FIG. 3b or other profiles as, for instance the one shown in FIG. 30, may be employed according to which the top side is plane and the bottom side is concave. Inasmuch as during operation it may occur that the inflow direction at the blades changes during a revolution, it may be expedient to employ an uncambered bi-concave profile, i.e., a wedge-shaped profile of which both the top and bottom sides are concave (FIG. 3d). This type of profile can operate where an up and down change in flow direction occurs.

For the sake of completeness it may be mentioned that the sharp leading edge of the wedge-shaped and biconcave shaped sections used for the blades of the tangential lift force propeller serves for separating the flow of Water at the suction surface of the profile, thus creating a water vapor bubble over the entire suction surface (super-cavitating flow). It is known that in the case of hydrofoils the effect of these profiles is very undesirable since it causes sudden changes in the lift force when crossing the cavitation barrier at higher speeds with inherent detrimental effects on the ship and the passengers. As tests have proved when employing super-cavitating foils as blades for the tangential lift force propeller in the watercraft according to the invention, the cavitation barrier can be crossed smoothly at an early stage of acceleration while at higher speeds there is no further speed limitation due to cavitation.

Inasmuch as it is desirable to obtain the condition of cavitation as early as possible, it may furthermore be advantageous to produce an artificial ventilation of the space of cavitation. As is well known with underwater hydrofoils having a cavitating profile, this is obtained by conveying atmospheric air through tubes or the like to the cavitation space, i.e., where the greatest underpressure occurs and consequently, cavitation starts first.

In connection with the present invention, atmospheric air may be introduced through corresponding conduits from the struts into the space of cavitation downstream with regard to the propeller. However, if desired, air may be conveyed into the rotating hub and may leave the latter through small bores and flow into the space of cavitation.

It may be mentioned in this connection that the water propellers do not under all circumstances have to work under water-rather, a partial emerging of the propellers is possible.

A particular advantage of the manner in which the lift is created in conformity with the present invention is to be seen in the fact that at rough sea, the propellers may,

without disadvantage, for a short period of time, completely emerge from the Water. In contrast to hydroplanes or ships with hydrofoils, no shock-like stresses wilI occur with the arrangement according to the present invention when the propellers again immerse into the water This is due to the fact that the rotation of the propeller: and the gradual lift-creating effect prevents severe shocks This means that a watercraft according to the present in vention can ride properly under conditions which would make a proper operation for speedboats and hydrofoil ships impossible.

It is, of course, to be understood that the present invention is, by no means, limited to the particular constructions shown in the drawing and above referred to, but alsc comprises any modifications within the scope of the appended claims.

What I claim is:

1. In combination with a watercraft having a hull and being free from normally submerged hydrofoils: strut means connected to and extending downwardly from said hull, a plurality of tangential lift force propeller means connected to said strut means below said hull for submersion in water during the operation of said watercraft, mechanical driving means, some of said tangential lift force propeller means being autorotating by their movement through the water for delivering the main lifting forces to lift the hull above the Water surface and only the remaining tangential lift force propeller means being drivingly connected to said mechanical driving means for propelling said watercraft in substantially horizontal direction and partially lifting said hull above the water surface while permitting at least the major portion of said propeller means to remain substantially continuously submerged in the water during the operation of said watercraft.

2. A watercraft according to claim 1, which includes control means operatively connected to said autorotating tangential lift force propeller means for selectively varying the angle of incidence thereof from a positive to a negative angle and vice versa to thereby selectively impart a positive and negative lift on said hull.

3. A watercraft according to claim 2, in which said control means is adapted to vary the positive and negative angle of incidence within the range of from 5 to 20.

4. A Watercraft according to claim 1, in which said autorotating tangential lift force propeller means are provided with blades having a supercavitating profile.

5. A watercraft according to claim 4, in which said blades have a bi-concave wedge-shaped cross section.

6. A watercraft according to claim 1, in which said tangential lift force propeller means is provided with blades arranged at an angle .of incidence 5 within the range 01 from 45 to said angle 9 being measured at 70% of the radius of said propeller means.

7. A watercraft according to claim 6, in which the blades are twisted from the tip towards the root thereof with increasing angles AS, said angles as being within the range of from 2 to 30.

References Cited by the Examiner UNITED STATES PATENTS 1,750,959 3/1930 Lake 114-665 2,408,788 10/1946 Ludington et al. 114-66.5 2,749,870 6/1956 Vavra 114-66.5 2,873,710 2/1959 Morel 114-1 3,077,173 2/1963 Lang 15S 3,125,981 3/1964 Reynolds 11466.5 X 3,146,751 9/1964 Von Schertel 114-665 FOREIGN PATENTS 431 7/ 1909 Great Britain.

MILTON BUCHLER, Primary Examiner.

T. MAI OR, Assistant Examiner. 

1. IN COMBINATION WITH A WATERCRAFT HAVING A HULL AND BEING FREE FROM NORMALLY SUBMERGED HYDROFOILS: STRUT MEANS CONNECTED TO AND EXTENDING DOWNWARDLY FROM SAID HULL, A PLURALITY OF TANGENTIAL LIFT FORCE PROPELLER MEANS CONNECTED TO SAID STRUT MEANS BELOW SAID HULL FOR SUBMERSION IN WATER DURING THE OPERATION OF SAID WATERCRAFT, MECHANICAL DRIVING MEANS, SOME OF SAID TANGENTIAL LIFT FORCE PROPELLER MEANS BEING AUTOROTATING BY THEIR MOVEMENT THROUGH THE WATER FOR DELIVERING THE MAIN LIFTING 